DK2297517T3

DK2297517T3 - Diaphragm wall in a large steam generator

Info

Publication number: DK2297517T3
Application number: DK09772046.0T
Authority: DK
Inventors: Martin Becker; Ralf-Udo Husemann
Original assignee: Mitsubishi Hitachi Power Systems Europe Gmbh
Priority date: 2008-07-02
Filing date: 2009-04-21
Publication date: 2016-08-29
Also published as: RS55108B1; EP2297517B1; WO2010000346A3; HUE030359T2; ES2587855T3; CY1117894T1; PL2297517T3; EP2297517A2; WO2010000346A4; PT2297517T; WO2010000346A2; ME02471B; LT2297517T; DE102008047784A1; HRP20161007T1

Description

The invention is directed towards a membrane wall of a utility steam generator comprising a plurality of tube-web-tube connections and/or finned-tube connections, in which the respective tubes of the tube-web-tube connection or the finned-tubes of the finned-tube connection are made from a steel material with ferritic-bainitic, martensitic or austenitic micro structure or a nickel-based alloy, and, in each case, the tubeconnecting web of the tube-web-tube connection or of the finned-tube connection is made, entirely or in combination, from a steel material with ferritic-bainitic, martensitic or austenitic micro structure or a nickel-based alloy.

Such a membrane wall is disclosed, for example, in US 5 092 278.

Since the middle of the 1990s, there have been numerous development projects in order to develop power stations with higher steam parameters. The goal is to develop so-called 700°C power stations. The background for this is, inter alia, a desired increase in the efficiency of coal-fired steam power stations, in order to compensate the reduction in efficiency of 10 to 15% resulting from a possible removal of CO2 from the waste gas.

One possibility for achieving an increase in efficiency is to increase the steam parameters. While, in the case of so-called 600°C power stations, these are disposed at 600°C and 280 bar and allow an efficiency of approximately 46%, in the case of a 700°C power station, the latter are disposed at 700°C and 350 bar steam pressure and then increase the efficiency to > 50%. However, for the use of increased steam parameters, the use of materials with higher heat stability and improved corrosion behaviour is necessary. Nickel-based alloys and martensitic steels containing 9-12% by weight chromium are regarded as suitable materials for the manufacture of membrane walls. However, materials made from nickel-based alloys are significantly more expensive than the austenitic materials previously used in power-station construction and are around 5 to 8 times more expensive than the conventional austenitic materials. Furthermore, the manufacturing costs for power-station components made from nickel-based alloys are higher than in the case of austenitic materials.

Alternative chromium-containing (9-12% by weight) martensitic materials must, in turn, necessarily be subjected to a heat treatment during the production of a membrane wall because of the welding required for this, which is associated with problems in the manufacture and the assembly of membrane walls made from these materials. In every welding process, the components consisting of such martensitic material must be preheated, and after every welding process, the respectively affected membrane element as a whole or the heat-influence zone of the weld seam must be annealed at approximately 700°C, in order to reduce the hardness. Furthermore, in the case of these martensitic steel materials with low chromium content, there is an increased occurrence of oxide in the interior of the tube, which can lead, during the operation of the power station, to increased tube-wall temperatures and, under some circumstances, to blockages of the tubes through flaking of the oxide.

These above problems and additional operational steps together with the previously apparently necessary use of high-cost materials mean that the investment costs for the 700°C power stations currently in the planning phase are around 15 to 25% higher than those of a conventional power station with the same output. Accordingly, solutions are being sought to reduce these investment costs through technical measures.

The invention is therefore based upon the object of providing a solution which allows the manufacture of a membrane wall suitable for use in a 700°C power station in a cost favourable manner with substantially identical technical effort for manufacturing.

This object is achieved by a membrane wall with the features of claim 1. Embodiments and further developments of the invention are specified in the dependent claims.

According to the invention, the membrane wall designated in the introduction is characterised in that the membrane wall comprises, at least in part, regions, in which different steel materials and/or nickel-based alloys are connected in a mutually adjacent manner as respective web-material or tube-material or as respective finned-tube material.

The invention is therefore based upon the idea that not all regions of a membrane wall need to be constituted completely with material which withstands the respective steam parameters. For example, it is possible to manufacture the tubes of the corresponding membrane-wall regions or portions from a nickel-based alloy material, but to connect the mutually adjacent tubes with a web made from more cost-favourable austenitic or optionally also martensitic material. In particular, however, it is therefore possible, in part, also to use more cost-favourable martensitic materials, by comparison with the “austenitic” nickel-based alloys, in regions, for the medium-conveying tubes, and, in particular, to connect mutually adjacent membrane-wall sub-segments with a web and/or tube made from austenitic nickel-based alloy material. In this context, in the assembly of the membrane-wall parts or membrane-wall sub-segments on the construction site, the heat treatment necessary in the case of martensitic material can be avoided, through so-called pre-tipping during the production of the corresponding membrane-wall parts or membrane-wall sub-segments in the workshop. In this context, a web or tube made from austenitic material, that is, a material with austenitic microstructure, especially an austenitic nickel-based alloy, is welded to the respective tubes and/or webs made from martensitic material, that is, made from a material with a martensitic microstructure. On the construction site, a corresponding web or a corresponding tube of an adjacent membrane-wall sub-segment, which also consist of a nickel-based alloy with austenitic micro structure and to the opposite end of which a tube or a web is welded, in turn, which optionally also consist of a nickel-based alloy material with austenitic structure, or a steel material with martensitic microstructure, is then welded, in turn, to this web or this tube. The weld seam connecting together the mutually adjacent webs or tubes of the two membrane-wall sub-segments does not then need to be heat treated. Because of the web or tube made from nickel-based alloy disposed in each case upstream of the tubes or webs with martensitic microstructure, the tube or web with martensitic microstructure remains without heat-influence zone and no heat treatment is necessary.

The regions with different materials are connected to one another with a welded connection, so that the invention provides in one embodiment that the mutually adjacent regions connected together, in each case made from different web- or tube-material or finned-tube material, are connected to one another with a welded connection.

In this context, it is further advantageous for the mechanical loading of the membrane wall if the different web- or tube-materials or fin materials comprise a similar coefficient of thermal expansion deviating from one another by a maximum of +/-20%. Because of the similar thermal expansion, it is ensured that no undesired, extraordinarily high tensile forces occur in the membrane wall during the operation of the steam generator.

While, in the case of membrane-wall areas which are exposed to the same steam parameters within a defined temperature range, wherein this generally involves regions of the membrane wall arranged substantially in a horizontal plane in utility steam generators, it is generally expedient and advantageous to manufacture large, two-dimensional regions of the membrane wall or of membrane-wall sub-segments with mutually adjacent web and tube materials or mutually adjacent finned-tube materials from a material with similar microstructure, for example, an austenitic or martensitic microstructure, in the transition region of membrane-wall regions which are exposed to different steam parameters, that is, in the case of membrane-wall regions arranged vertically above one another or in the case of horizontal, laterally adjacent regions made from a steel material with martensitic microstructure, it is, once again, expedient and advantageous to provide tube-web-tube connections and/or finned-tube connections, in which the web and at least one adjoining tube are constituted in each case from a different material, also with mutually different micro structure. Accordingly, in a further development, the invention provides that the different web- or tube-materials or fin materials comprise a different micro structure in each case.

Especially under these conditions, in the transition region of two membrane-wall regions arranged side-by-side in horizontal direction or of two membrane wall sub-regions with martensitic microstructure, in their substantial area, for example, in the first evaporator sub-region, in order to constitute a transition and connection region, for example, made from a combination of the material with martensitic micro structure and a material with austenitic microstracture, the invention is characterised in a further embodiment in that a web portion of a tube-web-tube connection or of a finned-tube connection extends only over a sub-region of the controlled web width. For example, the combination of a tube with martensitic microstructure and a web region made of nickel-based alloy material with austenitic microstructure welded to it can be produced by welding of the latter onto the tube in the assembly workshop, wherein the web then comprises only, for example, half the width of the web subsequently realised in the steam generator. In this sense, the controlled web width is understood as the total web width, in each case connecting two tubes to the finished membrane wall of the utility steam generator. With this embodiment of the invention, it is now possible to manufacture a connection to a tube-web counterpart or connecting piece on the construction site, which consists, for example, both in its web region and also in its tube region of a nickel-based alloy with austenitic microstructure, in that the two mutually abutting web regions, which together result in the controlled web width, are connected with a welded connection. Here, the heat-influence zone is therefore limited to the web region and no longer includes the adjacent tube, for example, comprising a martensitic microstructure, which has been previously connected in the workshop to the web with austenitic microstructure. In this manner, a heat treatment of these components comprising a martensitic microstructure is no longer necessary on the construction site.

In a combination of all possible sub-regions of the membrane wall in its finished operational configuration of the steam generator, the latter will therefore comprise both mutually adjacent regions made from the same materials, especially those with the same microstructure, and also mutually adjacent regions made from different material, especially also those with a different micro structure. The invention is therefore characterised in one embodiment in that the membrane wall comprises mutually adjacent regions with tube-web-tube connections or finned-tube connections made from different materials and mutually adjacent regions with tube-web-tube connections or finned-tube connections made from the same materials, especially with the same micro structure.

In one concrete embodiment, which can be realised in a cost-favourable manner, the membrane wall according to the invention is further characterised in that, in regions, especially in the discharge sub-region of the utility steam generator (preferably up to a region in which the respective tube withstands an operating-material limit temperature of approximately up to 550°C), the membrane wall consists of tube-web-tube connections or finned-tube connections in which web and tube or finned tube each consist of a steel material with ferritic-bainitic microstructure, especially 7CrMoVTiB10-10 or T24.

The designations used above and also the designations used in the following for steel types, or respectively for steel materials, correspond either to the conventional German material designations or to the nomenclature according to ASTM (American Society for Testing Materials), unless otherwise specified.

In the case of such a concrete steam generator, it can be further provided that, in regions, especially in a first evaporator sub-region of the utility steam generator above the discharge sub-region (in which the respective tube withstands an operating-material limit temperature within a range from approximately equal to 550°C to approximately equal to 600°C), the membrane wall consists of tube-web-tube connections or finned-tube connections in which web and tube or finned tube each consist of a martensitic steel material, especially VM12 or T92 or X10CrWMoVNb9-2.

Now it can be advantageous and expedient if, in some sub-regions of the membrane wall, especially in the first evaporator sub-region, the membrane wall is composed of individual membrane-wall segments or membrane-wall sub-segments, which consist to a quite considerable extent of tube-web-tube connections or finned-tube connections which are manufactured from a steel material with a martensitic microstructure, especially VM12 or T92. Now, in order to avoid a heat treatment or annealing of the welded seam region on the construction site, which is normally necessary with this martensitic steel material, these membrane-wall sub-segments can be provided in the workshop with a web region or a tube and/or tube- and web-pieces made of austenitic material, especially from a nickel-based alloy material, on their upper and/or lower side and/or on each of their longitudinal sides. These web regions or tubes or tube- and web-pieces are welded in the workshop to the upper or lower side and/or the longitudinal sides, and can be supplied for a heat treatment there. As a result of this process known as “pre-tipping”, during the assembly of these individual membrane-wall sub-segment regions on the construction site to form the complete membrane wall or sub-regions of the membrane wall, no materials with martensitic microstructure which are connected by means of a welded seam and would subsequently have to be subjected to a heat treatment or an annealing any longer directly adjoin one another. Heat treatments of these welded seam regions are no longer necessary on the construction site, although these membrane-wall sub-segments consist, in their quite substantial regions, of a material with martensitic micro structure.

The invention further provides that, especially in the first evaporator sub-region, the membrane wall comprises, at least in regions, tube-web-tube connections which each comprise at least one tube made of martensitic microstructure, especially VM12 or T92, with welded-on web or welded-on fin made from a nickel-based alloy, preferably with austenitic microstructure, especially A617 or HR6W.

In this context, it is not only possible that the web consists of a material with austenitic microstructure, and the adjacent tube of a material with martensitic microstructure. On the contrary, it is also possible that, at the outside, a tube of austenitic microstructure forms the termination, to which a web with martensitic micro structure has been welded in the workshop. The invention therefore further provides that, at least in regions, especially in the first evaporator region, the membrane wall comprises tube-web-tube connections which each comprise a web made of martensitic micro structure, especially VM12 or T92, with welded-on tube made of a nickel-based alloy, preferably with austenitic microstructure, especially A617 or HR6W.

In this context, according to a further embodiment of the invention, it is of particular advantage if the regions of welded-on webs or fins or tubes are constituted of nickel- based alloy on the longitudinal sides of a membrane-wall sub-segment consisting substantially of steel material with martensitic microstructure, especially VM12 or T92.

Alongside this embodiment relating to the lateral welding together of several membrane-wall sub-segments, the invention provides, for the welding together in the vertical direction of membrane-wall sub-segments disposed above one another, that, especially in the first evaporator sub-region, the membrane wall consists, at least in regions, of tube-web-tube connections or finned-tube connections, in which tube portions or finned-tube portions and/or web portions made of nickel-based alloy, preferably with austenitic microstructure, especially made of A617 or HR6W, are welded onto tube-web-tube portions or finned-tube portions made of a material with martensitic microstructure, especially VM12 or T92.

In this context, it is further particularly advantageous if the regions of welded-on tube-portions or finned-tube portions and/or web portions are constituted along the upper and/or lower side of a membrane-wall sub-segment of martensitic microstructure, especially VM12 or T92.

Membrane walls can be constructed and manufactured in a particularly cost-favourable manner if the latter is built up from individual membrane-wall sub-segments which are manufactured in the workshop and then welded to one another on the construction site. In this context, in order to use such membrane-wall sub-segments, which, to a substantial extent in their two-dimensional embodiment, comprise tubes and webs made from a material with martensitic microstructure, without the latter needing to be subjected to an annealing or heat treatment on the construction site after the welding, the invention is further characterised by a membrane-wall sub-segment consisting substantially of a steel material with martensitic microstructure, which comprises welded-on tube portions and/or web portions or finned-tube portions along its upper and lower side and welded-on web or fin regions or tubes made of nickel-based alloy material along its longitudinal sides.

In particular, on the longitudinal sides of a membrane-wall sub-segment, such an advantageous embodiment can also comprise more than one element made of nickel-based alloy material. The invention is therefore further characterised in that the portions or regions of the membrane wall or of the membrane-wall sub-segments comprising a tube consisting of nickel-based alloy material and/or a web consisting of nickel-based alloy material each comprise several tubes and/or webs.

Furthermore, in the case of such a utility steam generator, it can be provided that, in regions, especially in a second evaporator sub-region of the utility steam generator (in which the respective tube withstands an operating-material limit temperature in a range from approximately equal to 600°C to approximately equal to 620°C), the membrane wall consists of tube-web-tube connections or finned-tube connections, in which web and tube or finned tube each consist of a nickel-based alloy with austenitic micro structure, especially A617 or HR6W.

In this context, HR6W designates a steel originating from Japan which is designated there with this Japanese nomenclature.

Since a change of material with simultaneous variation of the microstructure takes place in the vertical direction of the membrane wall of the utility steam generator between the first evaporator sub-region and the second evaporator sub-region, it is advantageous according to a further embodiment of the invention, if, especially in the transitional region from the first evaporator sub-region to the second evaporator sub-region, the membrane wall consists, at least in regions, of a membrane-wall sub-segment made of a steel material with martensitic microstructure, especially VM12 or T92 with welded-on region or portion made of nickel-based alloy, preferably with austenitic microstructure, especially A617 or HR6W.

For regions arranged above this in the membrane wall of the finished utility steam generator, the invention provides that, in regions, especially in a first sub-region of the utility steam generator, with vertical tubing (in which the respective tube withstands an operating-material limit temperature in the range from approximately equal to 620°C to approximately equal to 600°C), the membrane wall consists of tube-web-tube connections or finned-tube connections in which web and tube or finned tube each consist of a nickel-based alloy, preferably with austenitic microstructure, especially A617 or HR6W.

Furthermore, for other regions, once again arranged vertically above this in the membrane wall, the invention provides that, in regions, especially in a second sub-region of the utility steam generator with vertical tubing, preferably in the region of the superheater (in which the respective tube withstands an operating-material limit temperature in the range of approximately equal to 600°C) the membrane wall consists, at least in regions, of tube-web-tube connections or finned-tube connections, which each comprise at least one tube made of a nickel-based alloy, especially A617 with welded-on web made from a nickel-based alloy different from it, especially HR6W, wherein both materials preferably comprise an austenitic microstructure.

Furthermore, for a last and uppermost region in the vertical direction of the finished membrane wall of the utility steam generator, it is provided in this context that, in regions, especially in a third sub-region of the utility steam generator (in which the respective tube withstands an operating-material limit temperature of up to approximately equal to 550°C), the membrane wall consists, at least in regions, of tube-web-tube connections or finned-tube connections, in which web and adjacent tube or mutually adjacent finned tubes each consist of a steel material with ferritic-bainitic microstructure, especially 7CrMoVTiB 10-10.

With such a vertically superposed arrangement of different sub-regions of the membrane wall of a utility steam generator, the invention further provides that, in the discharge sub-region and/or in the first evaporator sub-region and/or in the second evaporator sub-region and/or in the first sub-region with vertical tubing and/or in the second sub-region with vertical tubing and/or in the third sub-region of the utility steam generator, in each case, tube-web-tube connections or finned-tube connections are constituted, in which a web and a tube adjacent to it or two mutually adjacent web regions of the tube-web-tube connection or two mutually adjacent finned tubes of the finned-tube connection made from different steel material and/or different nickel-based alloy and/or from materials with different micro structure are welded to one another.

Furthermore, the invention provides in one embodiment that, in the discharge sub-region and/or in the first evaporator sub-region and/or in the second evaporator sub-region and/or in the first sub-region with vertical tubing and/or in the second sub-region with vertical tubing and/or in the third sub-region, in each case, tube-web-tube connections or finned-tube connections are constituted, in which a web and adjacent to it a tube or two mutually adjacent web regions of the tube-web-tube connection or two mutually adjacent finned-tubes of the finned-tube connection made from the same steel material and/or the same nickel-based alloy and/or from materials with the same micro structure are welded to one another.

Since the membrane wall also comprises sub-regions, especially those which are disposed at the same horizontal height of the membrane wall of the finished steam generator, the invention is also further characterised in that, in at least one of the evaporator sub-regions and of the sub-regions with vertical tubing, in each case, tube-web-tube connections or finned-tube connections are constituted, in which a web and a tube adjacent to it or two mutually adjacent web regions of the tube-web-tube connection or two mutually adjacent finned-tubes of the finned-tube connection in fact each made from different steel material and/or different nickel-based alloy, but with identical or similar micro structure are welded to one another.

The membrane wall composed of different sub-regions consequently also comprises transition regions from one sub-region to another sub-region arranged vertically above it. For these transition regions, the invention in one embodiment initially provides that, in the transition region from the discharge sub-region to the first evaporator sub-region and/or in the transition region from the first evaporator sub-region to the second evaporator sub-region and/or in the transition region from the second evaporator sub- region to the first sub-region with vertical tubing and/or in the transition region from the first sub-region with vertical tubing to the second sub-region with vertical tubing and/or in the transition region from the second sub-region with vertical tubing to the third sub-region of the utility steam generator, in each case, tube-web-tube connections or finned-tube connections are constituted, in which, in each case, a web and/or a tube of a sub-region with an adjacent web and/or tube of another sub-region made from different steel material and/or different nickel-based alloy and/or made from materials with different microstructure are welded to one another.

In this context, however, it can also be the case that, in the transition region from the second evaporator sub-region to the first sub-region with vertical tubing and/or in the transition region from the first sub-region with vertical tubing to the second sub-region with vertical tubing, in each case, tube-web-tube connections or finned-tube connections are constituted, in which, in each case, a web and/or a tube of a sub-region with an adjacent web and/or tube of another sub-region made from the same steel material and/or the same nickel-based alloy and/or made from a material with the same microstructure are welded to one another.

However, since it is also possible that, in fact, different materials are used, but these comprise the same microstructure, the invention finally also provides that, in at least one transition region between an evaporator sub-region or sub-region with vertical tubing and a sub-region with vertical tubing, in each case, tube-web-tube connections or finned-tube connections are constituted, in which, in each case, a web and/or a tube of a sub-region with an adjacent web and/or tube of another sub-region made from two respectively different steel materials and/or different nickel-based alloy, but with the same or similar micro structure are welded to one another.

It goes without saying that the above-named features, still to be explained in greater detail below, can be used not only in the respectively specified combination, but also in other combinations. The scope of the invention is defined only by the claims.

The invention is explained in greater detail below on the basis of the drawings. The drawings show in:

Fig. 1 in schematic view, a side wall of a membrane wall; and in

Fig. 2 in schematic plan view, a membrane-wall sub-segment.

Fig. 1 shows in a schematic view a side wall of a membrane wall 1 of a utility steam generator which consists of six sub-regions 2-7 arranged vertically above one another. In each case, the right-hand section of the image suggests the preferred material in each sub-region 2-7, from which, on the one hand, the respective tubes conveying the medium and, on the other hand, the web connecting two tubes or the web region welded onto a tube, is made in the exemplary embodiment. Furthermore, the micro structure of the respective material is specified in terms of materials technology for each region.

In the lowest sub-region, the discharge sub-region 2 of the utility steam generator, the membrane wall 1 consists of tube-web-tube connections in which both the tube and also the web consist of ferritic-bainitic steel material 7CrMoVTiB10-10. In the first evaporator sub-region 3 of the utility steam generator arranged vertically above this, in which the respective tube withstands an operating-material limit temperature in the range from approximately equal to 550°C to approximately equal to 600°C, the membrane wall 1 consists of a tube-web-tube connection, in which tube and web are manufactured from the steel material VM12, which comprises a martensitic micro structure. The operating-material limit temperature is understood as the temperature at which the respective tube achieves an operating life of at least 200,000 operating hours taking into consideration its oxidation behaviour (with regard to steam), its corrosion behaviour (with regard to flue gas/combustion chamber) and its strength behaviour (creep).

The different sub-regions of the membrane wall 1, namely, the discharge sub-region 2, the first evaporator sub-region 3, and the further, subsequently specified regions: second evaporator sub-region 4, first sub-region 5 with vertical tubing, second sub-region 6 with vertical tubing and third sub-region 7, are assembled on the construction site of a power station from individual segments prefabricated in the workshop to form the respective sub-region and the membrane wall as a whole. These individual membrane-wall sub-segments 8 are generally welded at their upper and lower side and at their opposing longitudinal sides to adjacent membrane-wall sub-segments 8’. While the adjacent segments 8’ welded onto the longitudinal sides are generally those of the same sub-region 2 to 7 of the membrane wall 1, adjacent segments from the respectively neighbouring sub-region 3 to 7 of the membrane wall 1 disposed vertically above the latter can, however, also be optionally connected by welding to the upper and lower side.

In the discharge sub-region 2 of the utility steam generator, exclusively a ferritic-bainitic steel material (7CrMoVTiB10-10) is used, so that here, segments of this sub-region 2 of the membrane wall 1 to be connected laterally to one another and above one another can be welded together without difficulty, without needing to take into consideration annealing or heat treatments.

By contrast, in the transition region from the lower discharge sub-region 2 to the evaporator sub-region 3 arranged vertically above it, a change of material from the ferritic-bainitic steel material 7CrMoVTiB10-10 to the martensitic steel material VM12 or T92, from which the evaporator sub-region 3 is substantially manufactured, takes place. Since martensitic materials must, on principle, be subjected to a heat treatment after welding, special measures are necessary in order to avoid such a heat treatment or annealing post-treatment in the case of the welding of individual segments of the membrane wall 1 on the construction site. In the transition region from the discharge sub-region 2 to the evaporator sub-region 3, but also within the evaporator sub-region 3, such a special measure consists in providing the individual membrane-wall sub-segments 8, 8’ of the first evaporator sub-region 3. In the evaporator sub-region 3, the membrane-wall sub-segments 8, 8’ consist of tube-web-tube connections or finned-tube connections 17 which are manufactured from the steel material VM12 or T92. Now, in order to connect these segments 8 on the construction site without further heat treatment to the segments 8’ adjacent to them, the individual segments 8, 8’ are preferably provided all round, that is, on their upper and lower side 11,12 and on both longitudinal sides, with tubes 13 or webs 14, 15, 16 or fins made from another material, welded-on in the workshop, in the present example, from the nickel-based alloy A617 or HR6W with austenitic micro structure. This so-called pre-tipping takes place in the workshop and, in this context, tubes 13 and webs 14 or fins with a length of approximately 100-150 mm made from A617 or HR6W are welded onto the upper and lower side 11, 12 of each segment 8, 8’ made from VM12 or T92 steel. One half web width, that is, one half of the controlled web width 15, 16 made from austenitic nickel-based alloy made from A617 or HR6W is preferably welded onto the longitudinal sides. Through this pre-tipping in the workshop, segments 8, which are then transported to the construction site as a transport unit are manufactured, which comprise an all-round connection made of nickel-based alloy, to which adjacent sub-segments 8’ of the membrane wall 1 can be welded, in each case by means of a weld seam. As a result of the pre-tipping and the welding-on of the elements made of nickel-based alloy, it is possible to carry out the required annealing and heat treatment of the welding zones necessarily occurring in this context in the workshop, and to manufacture the individual membrane-wall sub-segments 8 or segments of the membrane wall 1 forming a transport unit in this manner. By contrast, the connection to other similarly structured and manufactured membrane-wall sub-segments 8’ takes place on the construction site via weld seams which are implemented on the portions of the pre-tipped elements constituted from nickel-based alloy materials. As a result, the martensitic VM12 or T92 material is no longer thermally influenced, so that a heat treatment or annealing on the construction site is not necessary. In this manner, the evaporator sub-region 3 is assembled and fitted on the construction site.

In the vertical direction, in the transition region from the discharge sub-region 2 to the evaporator sub-region 3, tubes with welded-on or moulded-on fin or web made from the material 7CrMoVTiB10-10 with ferritic-bainitic micro structure of the discharge sub-region 2 are then welded, in each case, onto a pre-tipped portion made from a tube 13 and a fin or a web 14 made from nickel-based alloy, especially A617, of the segment or sub-segment 8, 8’ of the first, evaporator sub-region 3 to be arranged on it, comprising connections 17 made from tubes 9 made from VM12 or T92 and fins or webs 10 made from VM12 or T92. Accordingly, in the vertical direction, the material sequence: ferritic-bainitic 7CrMoVTiB 10-10-steel in the discharge sub-region 2, nickel-based alloy in the pre-tipped region and martensitic VM12 or T92 steel in the evaporator sub-region 3, is present.

Within the first evaporator sub-region 3, segments or membrane sub-segments 8, 8’ of this sub-region 3 of the membrane wall 1 arranged laterally side-by-side or above one another are welded along their pre-tipped web regions 15, 16, which generally amount to one half of the controlled width of one web. Here, a welded seam is therefore implemented in a similar manner along the respective pre-tipped web regions 15,16 made from nickel-based alloy material (A617 or HR6W). Once again, here also, since the welding here is in nickel-based alloy material, no influence of the martensitic micro structure of the tube or fin or web material adjacent on the other side of the web takes place.

While the individual segments 8, 8’ in the exemplary embodiment described above each end at the longitudinal sides with half webs 15, 16 made from nickel-based alloy material, it is also possible to have these longitudinal sides each end with a tube made from nickel-based alloy material. In the workshop, a tube made from nickel-based alloy material is then welded onto a final web made from martensitic steel. On the construction site, a segment 8’, which comprises a web made from nickel-based alloy material on the longitudinal side facing towards this tube, is then welded onto the side of it. Here also, a welding can be implemented on the construction site in which nickel-based alloy material is preferably constituted with austenitic microstructure.

Instead of the pre-tipping of short tubes 13 and webs 14 made from nickel-based alloy material, at the upper and lower side 11, 12 of every segment 8, 8’, it is also possible to apply only a weld-on weld or build-up weld or armour-plating onto the end-face edges of the martensitic tubes 9 and the martensitic webs 10. Such an armour-plating, welding-on or build-up welding then has the same function on the construction site and the same effect as the pre-tipped region made from the tubes 13 and webs 14 described above.

Such a welding-on, build-up welding or armour-plating can also be constituted on the longitudinal sides 15, 16 of every segment 8, 8’, and, in this context, can be applied to the lateral, longitudinal edge of a tube 9 or web 10 limiting the respective segment 8, 8’. In this case, the respective terminating web or the respective terminating tube made from nickel-based alloy material of the previously described exemplary embodiments is replaced by this welding-on, build-up welding or armour-plating.

It is naturally also conceivable to provide as a terminating piece a combination of tube and web or tube and armour-plating or web and armour-plating made from nickel-based alloy material. On a terminating region of a respective segment 8, 8’, which comprises several tubes and/or webs made of nickel-based alloy material, especially in the longitudinal edge regions 15, 16, this can be expedient dependent upon the application case and construction circumstances of the membrane wall 1 to be manufactured as a whole. A further possibility for the embodiment of the membrane sub-segments 8, 8’ is that the pre-tipping on the upper and lower side 11,12 comprises only the attachment of short tubes 13. A membrane sub-segment 8, 8’ pre-tipped in this manner on its upper and lower side 11, 12, which can otherwise be provided, according to one of the other possibilities, with a material portion made from nickel-based alloy material on its longitudinal sides, is manufactured in the workshop and then transported to the construction site. On the construction site, the pre-tipped tubes are then each welded to an adjacent membrane sub-segment and the inter-spaces remaining in the region of the webs are then closed with inserted plates made from nickel-based alloy material by welding on the construction site. Such small-scale welding, in which smaller regions of the respective membrane sub-segment 8, 8’ which consist of material with martensitic microstructure are then also welded, can also be provided with a corresponding annealing or heat treatment without difficulty on the construction site, or such an annealing or heat treatment measure can also be dispensed with in these small regions without endangering the overall strength and functionality of the membrane wall 1 as a whole.

Vertically above the first evaporator sub-region 3 of the steam generator, a second evaporator sub-region 4 of the steam generator is arranged, in which the respective tube withstands an operating-material limit temperature in the range from approximately equal to 600°C to approximately equal to 620°C. In this second evaporator sub-region, the tubes and the webs made of nickel-based alloy material A617 or HR6W each consist of austenitic microstructure. In the transition region from the first evaporator region 3 to the second evaporator region 4, in order to avoid the need to implement a heat treatment here on the construction site of the martensitic material VM12 or optionally T92 in the transition from the martensitic microstructure of the evaporator sub-region 3 to the austenitic microstructure in the evaporator region 4, the tubes 9 and webs 10 of the segments or sub-segments of the sub-region 3 made of VM12 or T92 steel material are pre-tipped in a similar manner to that described above with a tube piece 13 or web 14 or at least one partial web, which comprises a part of the overall width of the web subsequently provided as a whole, at least along its upper side 11, made from a tube material or web material with austenitic microstructure, especially made from the tube material and web material of the second evaporator sub-region 4. This means that, onto the tubes 9 and webs 10, those made from the austenitic material A617 or HR6W are welded in the workshop, during the production of the transition region from the first evaporator sub-region 3 towards the second evaporator sub-region 4. On the construction site, these webs 14 and tubes 13 are then welded to a corresponding web or at least web sub-region and to a corresponding tube made from the material A617 or HR6W of the second evaporator sub-region 4, wherein a heat treatment of the martensitic tubes 9 and webs 10 made from VM12 or T92 is then no longer necessary. A welding in the second evaporator sub-region 4 of wall parts or segments arranged laterally side-by-side is unproblematic, because the latter comprise an austenitic microstructure, and a special heat treatment after the welding of mutually adjacent membrane-wall sub-segments is not necessary on the construction site.

Above the second evaporator sub-region 4 of the utility steam generator, a first sub-region 5 of the utility steam generator with vertical tubing is then arranged, in which the respective tube withstands an operating-material limit temperature in the range from approximately equal to 620°C to approximately 600°C. In this sub-region 5 of the utility steam generator, the tubes and the webs consist of the nickel-based alloy A617 with austenitic micro structure. Since, in the transition region from the second evaporator sub-region 4 to the first sub-region 5 with vertical tubing, either no change of material or no change of micro structure occurs, mutually adjacent tube and web regions can be welded to one another here without difficulty. In particular, this is also possible because, in these regions, no materials with martensitic micro structure are used or present. A second sub-region 6 of the utility steam generator with vertical tubing, in which the respective tube withstands an operating-material limit temperature in the range of approximately equal to 550°C, then adjoins the first sub-region 5 with vertical tubing. In this region, in a similar manner, tubes and webs of the tube-web-tube connection do not consist of different nickel-based alloy materials, namely the nickel-based alloys A617 and HR6W, both of which, however, comprise an austenitic micro structure. Here also, the transition region between the first sub-region 5 and second sub-region 6 can therefore be realised by means of welded connections without difficulty. Finally, a further third sub-region 7 of the utility steam generator, in which the respective tube withstands an operating-material limit temperature in a range of up to approximately equal to 600°C, adjoins the second sub-region 6 of the steam generator with vertical tubing towards the top of the membrane wall 1. In this region, use is again made of the material 7CrMoVTiB10-10, which comprises a ferritic-bainitic microstructure, both for the tube and also for the web of the respective tube-web-tube connection. Such material can be welded to one another on the construction site without difficulty, but also to the nickel-based alloy material A617 and HR6W with austenitic microstructure, so that here also, special measures, such as the attachment and provision of pre-tipped material are not necessary.

Overall, with the measures described, a membrane wall 1 of a utility steam generator is created, which can be used in the new, so-called 700° power stations currently in the planning phase, but, in this context, does not comprise throughout more expensive nickel-based alloy materials. In part, different materials are used in the respective horizontal membrane-wall region between tube and fin, for example, in the membrane sub-segments of the second sub-region 6 of the utility steam generator with vertical tubing. In particular, however, membrane-wall sub-segments 8, 8’ are used which consist substantially over their area of a material with martensitic micro structure (VM12 in the evaporator sub-region 3) and are fitted with flue-gas-end exclusion regions made from the, by comparison different, material, especially comprising a higher strength and/or corrosion resistance and/or resistance to oxidation. In particular, these exclusion regions are constituted from pre-tipped elements made from a nickel-based alloy material (material). These regions can be constituted and arranged both on the longitudinal sides 15,16 and also on the respective upper and lower side 11, 12 of a membrane-wall sub-segment 8, 8’. When viewed over the vertical extension of the membrane wall 1, the membrane wall 1 also provides different materials, especially also the use of materials with ferritic-bainitic and martensitic microstructure. In order to avoid the heat treatment of workpieces or segments of the membrane wall made from material with martensitic micro structure subjected to a welding treatment in on-site operations, it is provided that, in the case of these sub-segments, through pre-tipping with corresponding material made from nickel-based alloy with austenitic microstructure, a possibility is created for the implementation of a welded connection, which no longer requires any heat treatment, because, in the case of the welding of the pre-tipped material on the construction site, the tube material made from martensitic VM12 or T92 connected via the pre-tipped material A617 is not thermally influenced in such a manner that an annealing or heat treatment would be necessary. The welding on of the pre-tipping material to the martensitic material takes place in the workshop during the manufacture of the respective segment or sub-segment, appropriate in its size as a transport unit. In the workshop, a heat treatment or annealing can be implemented without difficulty. Optionally, the welding of short seams on material with martensitic microstructure can also be implemented through the welding of web-plates on the construction site.

In the above, the embodiment of tube-web-tube connections is described. However, it is also possible to constitute membrane walls by means of finned tubes. Finned tubes are tubes which are constituted by a forming method, for example, hot extrusion, in such a manner that two diametrically opposed fin regions project from the cylindrical body. Finned tubes can therefore be fitted together to form a membrane wall, in that, in each case, one fin region of mutually adjacent finned tubes is welded to a fin region of the tube disposed opposite. In a similar manner, so-called omega or double-omega tubes can also be used.

Fig. 2 shows in schematic plan view a membrane-wall sub-segment 8 which is initially manufactured in a workshop in this form as a transport unit, then transported to the construction site of the utility steam generator and welded there to further, in each case, mutually adjacent membrane-wall sub-segments 8’ to form the membrane wall 1. The membrane-wall sub-segment 8 is such as is used in the first evaporator sub-region 3. It comprises substantially tubes 9 and webs 10 made from the steel material VM12 or T92 with martensitic micro structure arranged in the longitudinal direction alternating side-by-side and adjacent to one another. In the longitudinal direction of the tubes 9 and webs 10, on the upper and lower side 11, 12 of the membrane-wall sub-segment 8, in each case, short tube pieces 13 or web pieces 14 are each welded to a tube 9 or a web 10. The tube and web pieces 13, 14 comprise a length of approximately 100-150 mm. These tube and web pieces 13, 14 consist of a nickel-based alloy material, especially A617 or HR6W, which comprises an austenitic microstructure. The welding of the respective tubes 9 and webs 13 to the tube pieces 10 and web pieces 14 takes place in the workshop during the production of the membrane-wall sub-segment 8, so that the necessary heat treatment and annealing can be carried out there. On the longitudinal sides, in each case, a web strip 15, 16 is further welded onto the respective outside tube 9, which preferably comprises half the width of the controlled web width. These web regions 15, 16 are also constituted from the same nickel-based alloy material as the tube and web pieces 13, 14. Overall, the membrane-wall sub-segment 8 is accordingly pre-tipped all round, that is, on all its longitudinal sides and longitudinal edges, with a material made from nickel-based alloy material. Above these pre-tipped regions, the membrane-wall sub-segment 8 is then welded to a respectively adjacent membrane-wall sub-segment 8’, wherein the membrane-wall sub-segments 8, 8’ constituted within the first evaporator sub-region 3 are preferably constituted in an identical manner with regard to the material composition to the illustrated membrane-wall sub-segment 8. The connection of an identical membrane-wall sub-segment 8’ is suggested accordingly in Fig. 2. Via the connecting pieces 13, 14, the respective membrane-wall sub-segment 8 can then be welded, towards the top and/or towards the bottom, either with identically constructed membrane-wall sub-segments 8, 8’ or in the transition region, for example, from the first evaporator sub-region 3 to the second evaporator sub-region 4 arranged vertically above it, with a membrane-wall sub-segment of the second evaporator sub-region 4, in which the tube-web-tube connection consists entirely of a nickel-based alloy, for example, A617. However, in a similar manner, in the transition region from the first evaporator sub-region 3 to the discharge sub-region 2 constituted vertically below it, it is also possible to weld onto the pre-tipped region, tube-web-tube connections or finned-tube connections made from ferritic material, for example, 7CrMoVTiB10-10.

As a whole, the membrane wall 1 is built up in such a manner that it comprises at least one evaporator sub-region, in the present exemplary embodiment, the evaporator sub-region 3, which consists of a martensitic material. Overall, it is provided that, for the two-dimensional connecting regions 17, in at least one of the individual evaporator sub-regions 2-7, tube-web-tube connections or finned-tube connections are constituted, in which a tube made from VM12 or T12, which comprise materials with martensitic microstructure, is connected to a fin made from VM12 or T12 or T92 (martensitic micro structure) or A617 (nickel-based alloy, austenitic micro structure) or HR6W (nickel-based alloy, austenitic micro structure). Similarly, in one of the evaporator sub-regions 2-7, these two-dimensional membrane-wall regions can consist of a tube made from T24 with ferritic-bainitic micro structure or 7CrMoVTiB10-10 made from ferritic-bainitic microstructure, to which, in each case, at least one fin also made from T24 or 7CrMoVTiB10-10 or from VM12 or from 13CrMo4-4, is attached. A further possibility is to attach to a tube made from T92 comprising a martensitic microstructure, a fin made from T92 or VM12 or A617 or HR6W. Finally, two-dimensional membrane-wall regions in one of the evaporator sub-regions 2-7 can consist of a tube made from HR6W with fin also made from HR6W or A617 attached to it.

In particular, membrane-wall sub-segments are manufactured from the material combinations listed above, wherein, in the case of membrane sub-segments 8, 8’ comprising tubes made from VM12 or T92, pre-tipped regions are constituted at least on the longitudinal sides. Accordingly, the welding of two sub-segments 8, 8’ takes place along the pre-tipped region in the case of membrane-wall sub-segments in which the membrane-wall sub-segment 8 made from VM12, tubes or webs/fins with pre-tipped tubes or webs/fins made from A617 or HR6W is welded to a membrane-wall sub-segment with tubes or fins made from VM12 with pre-tipped tube or pre-tipped fins made from A617 or HR6W, especially, in the case of this lateral arrangement of pre-tipped regions, the fin region is constituted, in each case, with fins to be welded to one another on the respective membrane-wall sub-segment 8, 8’, of half the length of the total web width. A further possibility is also to pre-tip membrane walls consisting of YM12 material laterally with A617 or HR6W and to connect them to membrane-wall regions consisting of T24 with pre-tipped fins or pre-tipped web made from A617 or HR6W, wherein here also, the fin or the web preferably comprises half the controlled web width. It is also possible, in each case, to provide membrane-wall regions, which each consist of T92 material, with pre-tipped regions made from A617 or HR6W, or to weld membrane-wall regions which consist of T92 material with pre-tipped material regions comprising A617 or HR6W, in each case, to membrane-wall regions which consist of T24 material with laterally pre-tipped material made from A617 or HR6W (fins/web or optionally tube). Here also, the fins or the web can comprise half the controlled web width in each case.

For the connection of membrane wall elements disposed vertically above one another in the vertical direction, for the tube-tube connections, the material combinations VM12 tube, pre-tipped with tube pieces made from A617 or HR6W with tubes made from VM12, which similarly comprise pre-tipped tube portions made from A16 or HR6W, or the connection of VM12 tubes which are pre-tipped with tube pieces made from A617 or HR6W, with tubes made from T24, are provided for welding. Another material combination for this application case is to weld tubes made from T92 material with pre-tipped tube pieces made from A617 or HR6W to identically built up tubes made from T92 with pre-tipped tube pieces made from A617 or HR6W or to tubes made from T24. Further material combinations consist in welding tubes made from the material A617 directly to tubes made from A617, VM12, T92, T24 or HR6W, wherein the combination A617 with VM12 or T12 then necessitates an annealing or a heat treatment in the workshop. Finally, for this application purpose, the combination of tubes made from HR6W with tubes welded to them similarly made from HR6W, VM12, T92, T24 or A617 is also possible, wherein, here, once again, in the case of the connection to tubes made from VM12 or T92, an annealing must be implemented in the workshop.

Claims

A membrane wall (1) in a large steam generator comprising a plurality of pipe-bridge-pipe connections and / or pipes of pipe, wherein the respective pipes in the pipe-bridge-pipe connection or the pipes of the pipes are made of a steel material with ferritic-bainitic material, martensitic or austenitic microstructure or a nickel-based alloy, and the bridge in the tube-bridge-tube or veneer-tube connection, in each case connecting tubes, wholly or in combination consists of a steel material with ferritic-bainitic, austenitic or martensitic microstructure or a nickel-based alloy, wherein the diaphragm wall (1) exhibits at least in part areas where different steel materials and / or nickel-based alloys are connected to each other adjacent to each other as bridge or pipe material or as respective veneer material and where they are adjacent to each other and with each other. interconnected areas of each case differ t bridge or pipe material or veneer material is connected to each other by means of a welding joint, characterized in that the membrane wall (1) exhibits adjacent areas with pipe-bridge-pipe connections or veneer-pipe connections of different materials and adjacent areas with pipes - bridge-pipe joints or veneer joints of the same materials, especially with aggregate microstructure, and that the different bridge or pipe materials or veneer materials have a similar, maximum +/- 20% deviating heat expansion coefficient.

Membrane wall according to claim 1, characterized in that the different bridge or pipe materials or veneer materials each have a different microstructure.

Membrane wall according to claim 1 or 2, characterized in that a bridge section of a pipe-bridge-pipe connection or a fin-pipe connection extends only over a sub-region of the bridge regulation width.

Membrane wall according to one of the preceding claims, characterized in that the membrane wall (1) consists, in particular, in the discharge section area (2) of the large steam generator, of pipe-bridge-pipe connections or veneer pipe connections, each of which bridge and pipe or veneer pipe each. consists of a steel material with ferritic-bainitic microstructure, in particular 7CrMoVTiB10-10 or T24, or that the membrane wall (1) is regionally, especially in a first evaporator part area (3) of the large steam generator, above the discharge part area (3) consisting of pipe-bridge-pipe connections or veneer joints, wherein bridge and pipe or veneer each consist of a martensitic steel material, in particular YM12 or T92 or X10CrWMOVNb9-2.

Membrane wall according to one of the preceding claims, characterized in that the membrane wall (1), especially in the first evaporator part area (3), exhibits at least regionally, tube-bridge-pipe connections, each comprising at least one pipe (9) of martensitic microstructure, especially of VM 12 or T92, with welded bridge (15, 16) or welded fin of a nickel-based alloy, preferably with austenitic microstructure, especially of A617 or HR6W, or that membrane wall (1), especially in the first evaporator sub-region ( 3), at least regionally, exhibit tube-bridge-tube connections, each comprising a bridge (10) of martensitic microstructure, particularly of VM12 or T92, with welded tube of a nickel-based alloy, preferably with austenitic microstructure, especially of A617 or HR6W.

Membrane wall according to claim 5, characterized in that the areas of welded bridges (15, 16) or nickel-based alloy fins or tubes are formed on the longitudinal sides of a substantially martensitic microstructure steel material, in particular VM 12 or T92, consisting of membrane wall segment (8, 8 ').

Diaphragm wall according to one of the preceding claims, characterized in that the diaphragm wall (1), especially in the first evaporator part area (3), consists at least in the region of pipe-bridge-pipe connections or veneer-pipe connections, where on pipe-bridge pipe sections or veneer sections of a material having martensitic microstructure, especially of VM or T92, are welded pipe sections (13) or veneer sections and / or bridge sections (14) of a nickel-based alloy, preferably with austenitic microstructure, particularly of A617 or HR6W, preferably the regions of welded pipe sections (13) or veneer sections and / or bridge sections (14) are formed along the upper and / or underside (11, 12) of a membrane wall segment (8, 8 ') of martensitic microstructure, particularly of VM12 or T92.

Membrane wall according to one of claims 5 to 7, characterized by a membrane wall part segment (8, 8 ') consisting essentially of a steel material with martensitic microstructure and which exhibits along its upper and lower side (11, 12) welded pipe sections (13) and / or bridge sections (14) or veneer sections and along longitudinal sides welded piles of fines (15, 16), or consisting of nickel-based alloy material, preferably the sections or regions of the membrane wall (1) or membrane wall segments (8, 8 ') which exhibits a nickel-based alloy material tube and / or a bridge made of nickel-based alloy material, each comprising multiple tubes and / or bridges.

Membrane wall according to one of the preceding claims, characterized in that the membrane wall (1) consists, in particular, in another evaporator part area (4) of the large steam generator, of pipe-bridge-pipe connections or veneer pipe connections, wherein bridge and pipe or veneer pipe are each in particular, consists of a nickel-based alloy with austenitic microstructure, in particular of A617 or HR6W, or that the membrane wall (1), especially in the transition region from the first evaporator part region (3) to the second evaporator part region (4), consists at least of a membrane wall segment ( 8, 8 ') of a martensitic microstructure steel material, especially of VM 12 or T92, with welded region or sections of nickel-based alloy, preferably with austenitic microstructure, especially of A617 or HR6W, or that the membrane wall (1) is regionally, especially in a first sub-area (5) of the large steam generator with vertical pipe system, consists of pipe-bridge-pipe connections or veneer-pipe connections, where bridge and pipe or veneer tubes each consist of a nickel-based alloy, preferably with austenitic microstructure, especially A617 or HR6W, or that the membrane wall (1) is regionally, especially in another sub-region (6) of the large steam tube with vertical tubing system preferably in the region of the superheater; at least regionally, consists of pipe-bridge-pipe connections or veneer-pipe connections, each comprising a tube of a nickel-based alloy, in particular A617, with welded bridge of a relatively different nickel-based alloy, in particular HR6W, where both materials preferably exhibit a austenitic microstructure, or that the diaphragm wall (1), in particular, in a third subarea (7) of the large vapor generator, is at least regionally comprised of pipe-bridge-pipe connections or veneer-pipe connections, wherein bridge and adjacent pipes or adjacent pipes each especially consists of a steel material with ferri ten sk-bainiti sk microstructure, especially of 7CrMoVTiB 10-10.

Membrane wall according to one of the preceding claims, characterized in that in the discharge part area (2) and / or in the first evaporator part area (3) and / or in the second evaporator part area (4) and / or in the first part area (5) with vertical pipe system and / or in the second sub-area (6) with vertical pipe system and / or in the third sub-area (7) of the large steam generator, in each case, pipe-bridge-pipe connections or veneer-pipe connections are formed, where a bridge and an up adjoining pipes or two adjacent bridge areas of the pipe-bridge-pipe connection or two adjacent pipes of the veneer pipe connection of different steel material and / or different nickel-based alloys and / or materials of different microstructure are welded together.

Membrane wall according to one of the preceding claims, characterized in that in the discharge part area (2) and / or in the first evaporator part area (3) and / or in the second evaporator part area (4) and / or in the first part area (5) with vertical pipe system and / or in the second sub-area (6) with vertical pipe system and / or in the third sub-area (7), in each case, pipe-bridge-pipe connections or veneer pipe connections are formed, in which a bridge and an adjacent pipe or two adjacent bridge regions of the pipe-bridge-pipe connection or two adjacent pipes of the veneer connection of the same steel material and / or the same nickel-based alloy and / or of materials of the same microstructure are welded together.

Membrane wall according to one of the preceding claims, characterized in that in each case, at least one of the evaporator part areas (3, 4) and the sub-areas (5, 6) with vertical pipe system, pipe-bridge-pipe connections or veneer pipe connections are formed. a bridge and an adjacent pipe or two adjacent bridge regions of the pipe-bridge-pipe connection or two adjacent pipes of the pipe connection, more specifically in each case of different steel material and / or different nickel-based alloy, but with the same or uniform microstructure, are welded together.

Membrane wall according to one of the preceding claims, characterized in that in the transition region from the discharge sub-region (2) to the first evaporator section (3) and / or in the transition region from the first evaporator section (3) to the second evaporator section (4) and / or in the transition area from the second evaporator sub-area (4) to the first sub-area (5) with vertical pipe system and / or in the transition area from the first sub-area (5) with vertical pipe system to the second sub-area (6) with vertical pipe system and / or in the transition area from the second sub-area (6) with vertical pipe system to the third sub-area (7) of the large steam generator, in each case, pipe-bridge-pipe connections or veneer pipe connections are formed, where a bridge and / or a pipe of a sub-area (2 - 6) ) with an adjacent bridge and / or an adjacent pipe of another sub-area (3 - 7) of different steel material and / or different nickel-based alloy and / or material are with different microstructure in each case are welded together.

Membrane wall according to one of the preceding claims, characterized in that in the transition area from the second evaporator part area (4) to the first sub-area (5) with vertical pipe system and / or in the transition area from the first sub-area (5) with vertical pipe system to the second sub-area (6) with vertical pipe system is in each case formed pipe-bridge-pipe connections or veneer pipe connections, in which a bridge and / or a pipe of a sub-area (4, 5) with an adjacent bridge and / or an adjacent pipe of another sub-region (5, 6) of the same steel material and / or the same nickel-based alloy and / or of a material with the same microstructure in each case is welded together.

Membrane wall according to one of the preceding claims, characterized in that, in each case, at least one evaporator part area (4) or part area (5) with vertical pipe system and a part area (5, 6) with vertical pipe system is formed pipe-bridge-pipe connections or veneer pipe connections, wherein a bridge and / or a pipe of a sub-area (4, 5) with an adjacent bridge and / or a neighboring pipe of another sub-area (5, 6), in particular in each case of different steel material and / or different nickel-based alloy, but with the same or uniform microstructure, in each case welded together.